CAJ | 학술논문

关系数据库中空值存在不同的语义,并且会影响模糊查询结果.针对该问题,提出用标号来区分空值的语义,并且在EPTV逻辑的基础上,对关系运算和一些复杂的嵌套查询进行扩展,给出相关定义和计算方法.通过实例说明,与常规模糊查询相比,该方法能较好地反映空值对模糊查询结果的影响.
관계수거고중공치존재불동적어의,병차회영향모호사순결과.침대해문제,제출용표호래구분공치적어의,병차재EPTV라집적기출상,대관계운산화일사복잡적감투사순진행확전,급출상관정의화계산방법.통과실례설명,여상규모호사순상비,해방법능교호지반영공치대모호사순결과적영향.
Null values have different semantics in relational databases and influence the results of fuzzy queries.This paper distinguishes the different semantics of null values and attaches labels to these semantics.Relational operations and the complex nested queries are extended on the base of Extended Possibilistic Truth Values (EPTV) logic.Related definitions and calculation methods are proposed.Instances illuminate that the method can reflect the effects of different null values on query results compared with regular fuzzy queries.